In versions later than 5.0.11 or so, moving the item to inbox will train the antispam system. You should do that. You can then delete or file the message elsewhere. (What it's done in the background is forwarded the message as an attachment to the system ham-XXXXX account.)
View->Toolbars->Zimbra Support->Show Original will display the X-Spam headers, possibly giving some hint what's going on. If the score is above 8, then bayes training is not going to be enough. The 6.0.4 web client added per-user sender whitelists in Preferences->Mail->Junk Mail Options. |